The objective of this study was to correlate nitric oxide production with time of reperfusion of the post-ischemic feline small intestine. Epithelial permeability, quantitated as blood-to-lumen clearance of 51Cr-EDTA, following 1 hr of ischemia and 4 hr of reperfusion of the small intestine, increased approximately 10-fold. This increase was further augmented by L-NAME infusion between 60 and 120 min but not at 240 min. Ca(2+)-dependent nitric oxide synthase activity was reduced by approximately 50% at 3 and 4 hr of reperfusion, whereas Ca(2+)-independent nitric oxide synthase activity was undetectable throughout the experiment. Administration of L-arginine at the start of reperfusion attenuated the reperfusion-induced epithelial barrier dysfunction for the first 120 min but not at 180 or 240 min. Continuous infusion of a nitric oxide donor (CAS 754) following 1 hr of reperfusion reduced epithelial permeability at 4 hr of reperfusion. In conclusion, a reduction in nitric oxide production was observed with time of reperfusion, possibly due to reduced nitric oxide synthase levels.